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-XX:MaxMetaspaceSize: Sets the maximum size of Metaspace.

This option is available starting in JDK 8.

-XX:MetaspaceSize: Sets the initial size of Metaspace.

This option was available prior to JDK 8 but is no longer supported.

-XX:MaxPermSize: Sets the maximum size of the perm memory area.

-XX:PermSize: Sets the initial size of the Permanent Generation ( perm) memory area.

-Xmx: Sets the maximum size of the heap.

-Xms: Sets the minimum and initial size of the heap.

Parameters affecting the memory available to the JVM include:

How to determine ram allocation code#

If the application code is not the problem, increase the size of the Java heap to meet the load requirement. The article 10 Tips for using the Eclipse Memory Analyzer offers advice for analyzing heap dumps and memory leaks in the Eclipse Memory Analyzer.ДЄlso, see How do I analyze a Java heap dump for more details on analyzing the heap dump. The path to the garbage collection roots shows the reference chain that prevents the object on the heap from being garbage collected. The garbage collection roots are objects outside the heap and therefore are never collected.

Large retention by a single thread, perhaps the thread associated with the OutOfMemoryError.ДЄfter you've identified the source of the large retention, view the paths from the garbage collection roots to see what is keeping the objects alive.

Single objects that absorb all the heap memory allocated to the JVM.

Reasons for retaining large objects include: The problem might be caused by a memory leak in the application code otherwise, the problem is probably inadequate memory allocated for the application's peak loads. Sometimes, to find the cause of retention, you need to understand the application code and the circumstances that caused the out-of-memory error. The heap dump can show whether large objects were retained for a long time.

How to determine ram allocation how to#

Also, see How to monitor Java memory usage of heap/permanent generation and gc activities. You can also observe peak heap memory usage using JConsole. You can specify an alternative filename or directory with the -XX:HeapDumpPath option.

Having this option on is always recommended.Д«y default, the heap dump is created in a file called java_pidpid.hprof in the JVM's working directory. Configuring the option doesn't have any performance impact on your environment, so you can enable it in a production environment. The -XX:HeapDumpOnOutOfMemoryError option provides critical information about out-of-memory errors. The heap dump can help you find the cause. Detecting out-of-memory errorsД®nabling the -XX:HeapDumpOnOutOfMemoryError option generates a heap dump when an allocation from the Java heap could not be satisfied and the application fails with an OutOfMemoryError. Your production heap size should be at least 25% to 30% higher than the tested maximum to allow room for overhead. Next, test your application with the expected production load in a development environment to determine the maximum heap memory usage. Excessive allocation is often due to a memory leak. If garbage collections are happening too often or contributing to a significant percentage of your CPU, the first thing to do is check whether your application is allocating memory unnecessarily.

How to determine ram allocation full#

For instance, when full collection events happen too often, they cause high CPU usage on the application server, resulting in poor application request processing. Garbage collection can have a negative and unpredictable impact on Java application performance if it is improperly tuned. This article goes into more depth about memory use in the Java Virtual Machine (JVM) and how to control it.

The previous article introduced the stages and levels of garbage collection (including generational garbage collection) and showed how to check garbage collection behavior in your applications.

How to determine ram allocation series#

This is the second article in a series that explains garbage collection in Java and how to tweak it for optimal Java application performance.